MessageUI composers

Compose mail and messages with the iOS system UI

One.iOS.MFMailComposeViewController and One.iOS.MFMessageComposeViewController present Apple’s mail and message composers. Check canSendMail() or canSendText() first. Simulators and devices without configured services can report false. These are capability checks; One does not replace an unavailable composer with another mail or SMS app.

import { One } from 'one'

if (One.iOS.MFMailComposeViewController.canSendMail()) {
  const composer = new One.iOS.MFMailComposeViewController()
  composer.setToRecipients(['hello@example.com'])
  composer.setSubject('Hello')
  composer.setMessageBody('A message from the app', false)
  composer.mailComposeDelegate = {
    mailComposeController: (controller, result) => {
      // result.didFinishWith: cancelled, saved, sent or failed.
      // result.error preserves NSError domain, code and localizedDescription.
      void controller.dismiss()
    },
  }
  await composer.present()
}

if (One.iOS.MFMessageComposeViewController.canSendText()) {
  const composer = new One.iOS.MFMessageComposeViewController()
  composer.recipients = ['+15555550100']
  composer.body = 'Hello'
  composer.messageComposeDelegate = {
    messageComposeViewController: (controller, result) => {
      // result.didFinishWith: cancelled, sent or failed.
      void controller.dismiss()
    },
  }
  await composer.present()
}

The native controller remains owned by its delegate until the app dismisses it. present(animated = true) adapts UIViewController presentation to the current app presenter and resolves after presentation. Delegate callbacks report the composition result separately. dismiss(animated = true) resolves after closing the controller. Swift delegate argument labels become a JavaScript object after the controller argument.

Mail’s static canSendMail() returns the SDK capability. Message’s static canSendText(), canSendAttachments() and canSendSubject() return SDK capabilities; isSupportedAttachmentUTI(uti) checks an attachment type. Attachments use ArrayBuffer for native Data and file URL strings for native URL. Message attachment results preserve SDK success/failure booleans. attachments exposes native attachment URL and alternate filename dictionaries as { attachmentURL, attachmentAlternateFilename? } records.

Mail controller	Type	Description
`mailComposeDelegate`MFMailComposeViewControllerDelegate<MFMailComposeController> \| nullReceives result and optional NSError fields.	MFMailComposeViewControllerDelegate<MFMailComposeController> \| null	Receives result and optional NSError fields.
`setSubject`(subject: string) => voidSets the mail subject.	(subject: string) => void	Sets the mail subject.
`setToRecipients`(recipients: string[]) => voidSets primary recipients.	(recipients: string[]) => void	Sets primary recipients.
`setCcRecipients`(recipients: string[]) => voidSets copied recipients.	(recipients: string[]) => void	Sets copied recipients.
`setBccRecipients`(recipients: string[]) => voidSets blind copied recipients.	(recipients: string[]) => void	Sets blind copied recipients.
`setMessageBody`(body: string, isHTML: boolean) => voidSets plain text or HTML body.	(body: string, isHTML: boolean) => void	Sets plain text or HTML body.
`setPreferredSendingEmailAddress`(emailAddress: string) => voidSelects a preferred sending account.	(emailAddress: string) => void	Selects a preferred sending account.
`addAttachmentData`(attachment: ArrayBuffer, mimeType: string, fileName: string) => voidAdds native bytes with MIME type and filename.	(attachment: ArrayBuffer, mimeType: string, fileName: string) => void	Adds native bytes with MIME type and filename.
`present`(animated?: boolean) => Promise<void>Presents the configured system composer.	(animated?: boolean) => Promise<void>	Presents the configured system composer.
`dismiss`(animated?: boolean) => Promise<void>Dismisses the system composer.	(animated?: boolean) => Promise<void>	Dismisses the system composer.

Message controller	Type	Description
`messageComposeDelegate`MFMessageComposeViewControllerDelegate<MFMessageComposeController> \| nullReceives completion or cancellation.	MFMessageComposeViewControllerDelegate<MFMessageComposeController> \| null	Receives completion or cancellation.
`recipients`string[] \| undefinedRecipient addresses; undefined clears them.	string[] \| undefined	Recipient addresses; undefined clears them.
`body`string \| undefinedMessage body; undefined clears it.	string \| undefined	Message body; undefined clears it.
`subject`string \| undefinedSubject when supported; undefined clears it.	string \| undefined	Subject when supported; undefined clears it.
`attachments`MessageAttachment[]Native attachment URLs and alternate filenames.	MessageAttachment[]	Native attachment URLs and alternate filenames.
`disableUserAttachments`() => voidDisables attachment insertion by the user.	() => void	Disables attachment insertion by the user.
`addAttachmentData`( attachment: ArrayBuffer, typeIdentifier: string, filename: string ) => booleanAdds native bytes with a type identifier and filename.	( attachment: ArrayBuffer, typeIdentifier: string, filename: string ) => boolean	Adds native bytes with a type identifier and filename.
`addAttachmentURL`(attachmentURL: string, withAlternateFilename?: string) => booleanAdds a file URL with an optional display filename.	(attachmentURL: string, withAlternateFilename?: string) => boolean	Adds a file URL with an optional display filename.
`present`(animated?: boolean) => Promise<void>Presents the configured system composer.	(animated?: boolean) => Promise<void>	Presents the configured system composer.
`dismiss`(animated?: boolean) => Promise<void>Dismisses the system composer.	(animated?: boolean) => Promise<void>	Dismisses the system composer.

Mail configuration requires a device on which mail can be sent. Unsupported mail and message presentation reject with E_MAIL_COMPOSE_UNAVAILABLE and E_MESSAGE_COMPOSE_UNAVAILABLE. Presentation without an active presenter rejects with E_UIKIT_PRESENTER; duplicate presentation and overlapping transitions reject with E_UIKIT_PRESENTED and E_UIKIT_TRANSITION.

The simulator fixture checks real capability results and unsupported presentation without a success callback. Actual supported composer content, attachment acceptance, sending, saving and user cancellation require device acceptance. A delegate callback injected by a probe proves callback routing only.

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